During casting of liquid resins for ophthalmic or specialty optics applications, the resin is introduced into a cavity formed by two mold pieces and polymerized into a solid object. The final object replicates the shape of the mold faces. Traditional molds that are employed for thermal or radiation polymerization of liquid resins are made of either glass or metals. These materials are chosen since they are usually inert to most liquid resins, non-porous, durable, and have high thermomechanical stability, thereby allowing a large number of castings to be made before replacement is necessary.
One major problem with the use of glass or metal molds is their cost. Each mold piece requires individual machining and/or polishing which is relatively expensive. Even when slumping is used to produce acceptable glass molds, their production cost remains high. Although, metal or glass molds are durable under normal operating conditions, they may be easily damaged if mishandled. Chipping, cracking, and scratching of the mold face are simple manifestations of mishandled molds. It is therefore extremely desirable to develop molds that may be mass manufactured inexpensively.
An inexpensive alternative to glass or metal is plastic molds. However, plastic suffers from several disadvantages compared with glass or metal. For example, certain liquid resins may soften, etch and/or react with the plastic mold material rendering the mold unsuitable for preparing optical devices. Also, plastic is not as durable particularly with respect to scratching, and has much poorer thermomechanical stability than glass or metal. Plastic also has a higher thermal expansion coefficient over glass or metal, which may cause deformation of the mold face particularly if the curing temperatures are high. However, since plastic items can be produced very inexpensively using traditional processes such as injection molding, the use of plastic molds may be viable for certain applications.
Accordingly, it is an object of the present invention to provide a plastic mold for casting of ophthalmic or specialty lenses, or other optical objects.
It is a further object of the present invention to provide plastic ophthalmic molds coated with a formulation that is durable, adheres strongly to plastic substrate during the curing process, but provides release capability.
It is another object of the present invention to provide a method of making a plastic mold for casting of ophthalmic or specialty lenses, or other optical objects.